31 Mar

Magnetic Cranes and Grab Cranes

Magnetic cranes are referred to a special type and designed for lifting and transporting ferromagnetic materials (scrap metals, chips, sheets, molds for casting and so on). These cranes are equipped with cargo electromagnets, hung on a hook suspension or traverse (on a floppy or hard suspension) located in the longitudinal or transverse direction of the bridge.

Magnetic cranes production is a prerogative of large scale businesses: the United Kingdom example is Granada Material Handling, a prosperous company with 14 years of track record, focusing on production, as well as lifting equipment inspection and lifting equipment services. The company’s pipeline gives birth to a variety of magnetic equipment types: here is a specifications breakdown (approximate data, the average values and serial production machines are considered).

  • Lifting capacity: 5 to 40 tons.
  • Lifting speed: 14-20 m/min.
  • Trolley crane speed: 70-120 m/min.

The most common among these cranes are the systems with single wall beams and auxiliary farms, as well as double-girder box-like structure with high resistance to fatigue.

Magnetic crane consists of a bridge with the mechanism of movement of one or two trucks with lifting mechanism and movement, lifting magnets and cab, hung from the metal bridge.

Mechanisms of movement of cranes and trucks do not have differences in comparison with the mechanisms of overhead cranes for general purposes. On the trolley bridge crane mounted magnetic lifting mechanism and movement. Such systems are typically comprised of the magnetic cranes, lift mechanism and cable drums, from which the cable is supplied to the electromagnet. As a rule, the use of the drum is allowed at a high altitude climb.

Cable drum receives the rotation from the drum lifting mechanism via a chain drive. When working without a cable drum magnet is turned off. A cable drum has a shaft ring collector mounted on the same side. The cable is connected to the rotating parts of the ring collector. Laying of cables in one layer with a uniform step of winding produces cable layer, which moves along the screw. Screw rotation is transmitted from the cable drum via a gear.

Grab crane mechanism in action

Grab cranes are designed for lifting and transporting bulk and lump materials. These lifting devices offer a variety of grabs designs. Grab cranes may have grab winch with two drums, one of which is designed for winding the rope closing at the closing of the jaws (NO), and the other – for winding the supporting rope (lifting). Lifting drum works in conjunction with the closing one when lifting and lowering the grab.

The load capacity of these cranes is determined by the total weight of the grapple and cargo.

In bridge grab cranes the dominant distribution is placed on winch with independent drums. The winch is mounted on a trolley bridge crane and consists of two identical single-drum winches: closing and supportive. These winches are respectively closing and supporting drums, motors, gears and brakes.